At which OSI layer do firewalls primarily operate?

Firewalls primarily operate at the Network Layer (Layer 3) and the Transport Layer (Layer 4) of the OSI model. At Layer 3, firewalls analyze the IP addresses of the packets to make decisions about whether to allow or block traffic. This enables them to filter packets based on the source and destination IP addresses, which is crucial for controlling network traffic and determining whether it is permissible.

At Layer 4, firewalls extend their functionality to inspect the transport layer protocols, such as TCP and UDP. This layer allows firewalls to monitor connections and maintain session states, enabling them to apply rules based on port numbers and connection states (e.g., establishing or terminating a session). This is particularly important for implementing more granular control over what traffic is allowed, as it ensures that only valid packets as per the established rules can pass through.

While firewalls can also possess capabilities that extend further into Layer 7 (the Application Layer), their core functionalities and primary operations are rooted in Layers 3 and 4. Layer 7 firewalls tend to focus on filtering traffic based on application-layer data, but such characteristics are additional features rather than the primary operation that defines the firewall's basic functionality in network security. The primary roles of fire